Skinfold Body Fat Calculator

This calculator relies on the established Durnin-Womersley skinfold protocol, which uses the sum of four skinfold sites: the tricep, bicep, subscapular, and suprailiac. First, the calculator takes the common logarithm (base 10) of the combined millimeter sum. Next, depending on your biological sex and age bracket, it applies a specific linear regression equation to estimate body density (Db). For instance, a typical male equation takes the form: Db = C1 - (C2 * log10(Sum)), where C1 and C2 are constants specific to that demographic group. Finally, your estimated body density is converted into a body fat percentage using the Siri equation: Body Fat % = [(495 / Density) - 450] / 100.

Consider a 28-year-old male who wants to measure his body fat percentage using skinfold calipers. Suppose his measurements are as follows: tricep = 10 mm, bicep = 6 mm, subscapular = 12 mm, and suprailiac = 14 mm. First, we sum these values: 10 + 6 + 12 + 14 = 42 mm. Next, we compute the base-10 logarithm of 42, which is approximately 1.6232. Using the male age group 20-29 formula (Density = 1.1631 - (0.0632 * 1.6232)), we find his body density equals 1.1631 - 0.1026 = 1.0605 g/cm³. Finally, applying the Siri equation: [(495 / 1.0605) - 450] / 100 yields a body fat percentage of approximately 16.7%.

To ensure consistent and reliable body fat readings, always use a calibrated skinfold caliper designed to apply a constant tension of 10 g/mm². Take all measurements on the right side of the body while the skin is completely dry and lotion-free. It is also best to have the same trained professional take repeated readings at each anatomical site to minimize inter-tester variability.